Unidirectional Growth Research Articles

Plasma membrane and cytoplasmic compartmentalization: a dynamic structural framework required for pollen tube tip growth.

Rapid, unidirectional pollen tube tip growth is essential for fertilization and is widely employed as a model of polar cell expansion, a process crucial for plant morphogenesis. Different proteins and lipids with key functions in the control of polar cell expansion are associated with distinct domains of the plasma membrane (PM) at the pollen tube tip. These domains need to be dynamically maintained during tip growth, which depends on massive secretory and endocytic membrane trafficking. Very little is currently known about the molecular and cellular mechanisms responsible for the compartmentalization of the pollen tube PM. To provide a reliable structural framework for the further characterization of these mechanisms, an integrated quantitative map was compiled of the relative positions in normally growing Nicotiana tabacum (tobacco) pollen tubes of PM domains 1) enriched in key signaling proteins or lipids, 2) displaying high membrane order, or 3) in contact with cytoplasmic structures playing important roles in apical membrane trafficking. Previously identified secretory and endocytic PM domains were also included into this map. Internalization of regulatory proteins or lipids associated with PM regions overlapping with the lateral endocytic domain was assessed based on brefeldin A (BFA) treatment. These analyses revealed remarkable aspects of the structural organization of tobacco pollen tube tips, which 1) enhance our understanding of cellular and regulatory processes underlying tip growth, and 2) highlight important areas of future research.

Amine-impregnated elastic carbon nanofiber aerogel templated by bacterial cellulose for CO2 adsorption and separation

Carbon aerogel has become a promising electrode material for CO2 capture and capacitor due to its large specific surface area, well-developed pore structure, adjustable porosity and ultra-high specific power. However, most of the carbon-based materials suffer from poor mechanical properties, low recycling efficiency, and low adsorption capacity, making it difficult to be put into industrial applications on a large scale. Bacterial cellulose (BC) has an ultra-fine reticular structure, a modulus of elasticity that is several to more than ten times that of typical plant fibers, and high tensile strength. In this paper, BC was treated by unidirectional freeze-drying method, and the aerogels with ordered honeycomb pore structure were constructed by unidirectional growth of ice crystals, and the pyrolytic chemical properties of BC were adjusted by using (NH4)2SO4, which effectively prevented the shrinkage and deformation of materials during carbonization, and successfully prepared elastic nanocarbon fiber aerogels. At the same time, the introduction of (NH4)2SO4 made the material realize N doping in the carbonization process, providing more adsorption sites, which was conducive to the adsorption of CO2. Finally, the carbon fiber nanoaerogel was modified by TEPA to further improve its adsorption selectivity for CO2. The prepared elastic carbon nanofiber aerogel (CBCNT) has high CO2 adsorption performance and high selectivity, and its CO2 capture capacity is up to 4.88 mmol/g. At the same time, its capacitance also reached 246F/g.

Investigating the effect of path planning strategies on 3D metallic structure deposited using robotic WAAM

Wire Arc Additive Manufacturing (WAAM) is an advanced technique for producing medium-to-large-sized components, offering high deposition rates and low equipment costs. Path planning strategies are critical in determining grain growth direction and achieving isotropic properties in the components. This study introduces a novel path planning strategy, the switchback mode, to mitigate unidirectional grain growth and enhance the mechanical properties of WAAM-deposited components. ER-4043 aluminium alloy walls were deposited using the switchback mode and compared with the conventional bi-directional path planning strategy. The findings reveal that different path planning strategies result in variations in layer size, surface morphology, microstructure, residual stress, microhardness, wear resistance, and tensile properties. Notably, the switchback mode demonstrated superior mechanical strength compared to the bi-directional mode, with yield strength (YS) increasing from 90.2 MPa to 113.9 MPa, ultimate tensile strength (UTS) from 148.8 MPa to 178.7 MPa, and elongation percentages from 18.4 % to 21.3 %. Furthermore, the residual stress changed from tensile to compressive when switching from bi-directional to switchback mode.

Super-Elastic and Temperature-Tolerant Hydrogel Electrodes for Supercapacitors via MXene Enhanced Ice-Templating Synthesis.

Developing flexible energy storage devices with good deformation resistance under extreme operating conditions is highly desirable yet remains very challenging. Super-elastic MXene-enhanced polyvinyl alcohol/polyaniline (AMPH) hydrogel electrodes are designed and synthesized through vertical gradient ice templating-induced polymerization. This approach allows for the unidirectional growth of polyaniline (PANI) and 2D MXene layers along the elongated arrayed ice crystals in a controlled manner. The resulting 3D unidirectional AMPH hydrogel exhibits inherent stretchability and electronic conductivity, with the ability to completely recover its shape even under extreme conditions, such as 500% tensile strain, 50% compressive strain. The presence of MXene in the hydrogel electrode enhances its resilience to mechanical compression and stretching, resulting in less variation in resistance. AMPH has a specific capacitance of 130.68 and 88.02mFcm-2 at a current density of 0.2 and 2mAcm-2, respectively, and retains 90% and 70% of its original capacitance at elongation of 100% and 200%, respectively. AMPH-based supercapacitors demonstrate exceptional performance in high salinity environments and wide temperature ranges (-30-80°C). The high electrochemical activity, temperature tolerance, and mechanical robustness of AMPH-based supercapacitor endow it promising as the power supply for flexible and wearable electronic devices.

Unidirectional growth of molybdenum dioxide nanoflakes on C-sapphire substrate via buffer layer induction

Unidirectional growth, a novel and promising approach, is a key method for synthesizing large-scale single crystals of ultra-thin materials. In this study, we present a unique and convenient method for the growth of molybdenum dioxide (MoO2) nanoflakes on a c-sapphire substrate, achieving uniform orientation. Specifically, the MoO2(100) and MoO2 < 021¯> are aligned parallel to sapphire(0001) and sapphire<12¯10>, respectively. A crucial observation in our study is the presence of a buffer layer between the as-grown MoO2 and c-sapphire. This buffer layer is essential in overcoming the limitation of lattice mismatch, thereby facilitating the unidirectional growth of MoO2. The introduction of reductants, such as H2 and sulfur vapor, is critical for the formation of this buffer layer. Electrical measurements indicate that the electrical conductivity of the as-grown MoO2 nanoflake is approximately 3.91 × 106 S/m at 300 K, which is comparable to other metallic nanomaterials. In addition, magnetotransport measurements reveal that the as-grown MoO2 nanoflakes exhibit a temperature-dependent linear magnetoresistance (MR) under magnetic fields. These findings not only demonstrate a method for the unidirectional growth of MoO2 on the c-sapphire substrate but also have significant implications for the application of MoO2 in transparent electrodes and the fabrication of integrated devices based on MoO2.

Numerical simulation study on opening blood–brain barrier by ultrasonic cavitation

Experimental studies have shown that ultrasonic cavitation can reversibly open the blood–brain barrier (BBB) to assist drug delivery. Nevertheless, the majority of the present study focused on experimental aspects of BBB opening. In this study, we developed a three-bubble-liquid-solid model to investigate the dynamic behavior of multiple bubbles within the blood vessels, and elucidate the physical mechanism of drug molecules through endothelial cells under ultrasonic cavitation excitation. The results showed that the large bubbles have a significant inhibitory effect on the movement of small bubbles, and the vibration morphology of intravascular microbubbles was affected by the acoustic parameters, microbubble size, and the distance between the microbubbles. The ultrasonic cavitation can significantly enhance the unidirectional flux of drug molecules, and the unidirectional flux growth rate of the wall can reach more than 5 %. Microjets and shock waves emitted from microbubbles generate different stress distribution patterns on the vascular wall, which in turn affects the pore size of the vessel wall and the permeability of drug molecules. The vibration morphology of microbubbles is related to the concentration, arrangement and scale of microbubbles, and the drug permeation impact can be enhanced by optimizing bubble size and acoustic parameters. The results offer an extensive depiction of the factors influencing the blood–brain barrier opening through ultrasonic cavitation, and the model may provide a potential technique to actively regulate the penetration capacity of drugs through endothelial layer of the neurovascular system by regulating BBB opening.

Investigating laser power in AM-LMD process on the Inconel 718 powder deposited profile microstructure, aiming to repair gas turbine blades

ABSTRACT The purpose of this study was to evaluate the feasibility of repairing defective turbine blades made of Inconel 738 using additive manufacturing called laser metal deposition with the use of Inconel 718 powder. The deposition process was conducted on substrates using varying laser power, 150, 250 and 350 (W). The experimental results indicate that as the laser power is raised, there is a corresponding increase in the average of substrate melting depth, 33.42–405.12 (µm), the average of interface thickness, 2.85–10.20 (µm) and the amount of dilution, 0.036–0.684 (%). The substrate's volume percentage and the average size of the γ’ phase exhibit larger values prior to the deposition procedure compared to the subsequent stages. The augmentation of laser power resulted in a proportional rise in both the volume percentage and average size of the γ’ phase within the substrates. At the location near the interface of the first layer, graining is preferentially in the direction of heat transfer and crystal growth. A narrow unmixed zone was formed along the melting line in the substrate and first layer’s interface, that whit increased laser power, area of this zone decreased, 7.27 to almost 0 (µm). As the layers approach the surface, the grains become unidirectional and coaxial growth. Increasing the laser power increased the average grain size of the layers.

Factors Impact of the Stock Market Performance During the Covid-19 Crisis

Research originality: This research adds the exchange rate variable and the use of the Vector Autoregressive (VAR) model that can add to the financial literature.Research Objectives: This study examines how macroeconomics can impact a business during a crisis. The stock market has associated access with new COVID-19 cases and new deaths in Indonesia. During the pandemic, the exchange rate is critical, so this study observes the exchange rate of IDR against USD. This paper investigates the relationship between new cases, new deaths, and the exchange rate with the stock market index.Research Methods: The study retrieves the daily data from March 2, 2020, to June 30, 2022, from Our World in Data, Indonesia's stock exchange, and Indonesia's Statistic Central Bureau. We have used the ADF, Vector Autoregressive (VAR) Model, impulse response function, and the Toda Yamamoto causality test. Empirical Results: The findings reveal a significant negative impact of new COVID-19 cases, new deaths, and exchange rates on the stock market. Toda Yamamoto's causality analysis reveals substantial evidence of unidirectional daily growth of new COVID-19 deaths in the stock market and a bidirectional causality of new COVID-19 cases and new COVID-19 deaths.Implications: The policy implications of this study are to stabilize markets, impact overall financial stability, support entrepreneurship, and develop a competitive market environment that can encourage innovation. JEL Classification: C5, E31, F31How to Cite:Goh, T. S., Henry, H., &amp; Erika, E. (2024). Factors Impact of the Stock Market Performance During the Covid-19 Crisis. Etikonomi, 23(1), 47 – 62. https://doi.org/10.15408/etk.v23i1.32005

Colloidal Multi-Dot Nanorods.

Colloidal nanorod heterostructures consisting of multiple quantum dots within a nanorod (n-DNRs, where n is the number of quantum dots within a nanorod) are synthesized with alternating segments of CdSe "dot" and CdS "rod" via solution heteroepitaxy. The reaction temperature, time dependent ripening, and asymmetry of the wurtzite lattice and the resulting anisotropy of surface ligand steric hindrance are exploited to vary the morphology of the growing quantum dot segments. The alternating CdSe and CdS growth steps can be easily repeated to increment the dot number in unidirectional or bidirectional growth regimes. As an initial exploration of electron occupation effects on their optical properties, asymmetric 2-DNRs consisting of two dots of different lengths and diameters are synthesized and are shown to exhibit a change in color and an unusual photoluminescence quantum yield increase upon photochemical doping.

Regulation of tissue growth in plants - A mathematical modeling study on shade avoidance response in Arabidopsis hypocotyls.

Plant growth is a plastic phenomenon controlled both by endogenous genetic programs and by environmental cues. The embryonic stem, the hypocotyl, is an ideal model system for the quantitative study of growth due to its relatively simple geometry and cellular organization, and to its essentially unidirectional growth pattern. The hypocotyl of Arabidopsis thaliana has been studied particularly well at the molecular-genetic level and at the cellular level, and it is the model of choice for analysis of the shade avoidance syndrome (SAS), a growth reaction that allows plants to compete with neighboring plants for light. During SAS, hypocotyl growth is controlled primarily by the growth hormone auxin, which stimulates cell expansion without the involvement of cell division. We assessed hypocotyl growth at cellular resolution in Arabidopsis mutants defective in auxin transport and biosynthesis and we designed a mathematical auxin transport model based on known polar and non-polar auxin transporters (ABCB1, ABCB19, and PINs) and on factors that control auxin homeostasis in the hypocotyl. In addition, we introduced into the model biophysical properties of the cell types based on precise cell wall measurements. Our model can generate the observed cellular growth patterns based on auxin distribution along the hypocotyl resulting from production in the cotyledons, transport along the hypocotyl, and general turnover of auxin. These principles, which resemble the features of mathematical models of animal morphogen gradients, allow to generate robust shallow auxin gradients as they are expected to exist in tissues that exhibit quantitative auxin-driven tissue growth, as opposed to the sharp auxin maxima generated by patterning mechanisms in plant development.

Monte Carlo simulation of planar GaAs nanowire growth

The Monte Carlo model for the planar GaAs nanowire growth via the vapor–liquid-solid mechanism on GaAs substrate using a gallium droplet as a catalyst is realized. The effect of temperature, Ga and As2 deposition rates, substrate orientation and surface properties on the morphology of planar GaAs nanowires is considered. It is shown, that at the initial stages of nanowire growth, a 3D GaAs crystal is formed under a gallium droplet, which sets the nanowire growth direction. The range of temperatures and deposition rates of gallium and arsenic, which ensure the planar nanowire formation on the GaAs(111)A surface, is determined. The investigation of surface properties influence on the nanowire morphology showed that the arsenic diffusion influx into a gallium droplet is of critical importance for the planar GaAs nanowire growth. Ways for achieving a unidirectional growth of planar nanowires on singular and vicinal GaAs surfaces are proposed.

Disequilibrium reaction pathways and the twin-mediated growth of tabular forsterite during contact metamorphism of quartz-bearing dolomite

The forsterite zone of the Ubehebe Peak contact aureole, Death Valley, USA consists of an outer zone of tabular/jack-straw olivine and an inner zone of subequant polyhedral olivine. Subequant polyhedral forsterite crystals close to the intrusion are small and tabular forsterite crystals farther away are larger. To investigate the formation of the two morphologies, forsterite growth experiments were conducted in cold seal pressure vessels in the CaO-MgO-SiO2-CO2-H2O system. Forsterite precipitation follows a disequilibrium reaction pathway made of three reactions: [1] tabular forsterite growth from quartz and dolomite, [2] forsterite growth from tremolite dissolution, and [3] subequant polyhedral forsterite growth from tabular forsterite dissolution. Initially, quartz reacts with dolomite to simultaneously form twinned tabular forsterite and tremolite. As quartz reacts away, forsterite precipitation continues at a slower rate through tremolite dissolution. A second generation of forsterite then precipitates on top of some tabular forsterite but has different habit and tracht. Once all the tremolite reacts away, subequant polyhedral forsterite precipitation continues at an even slower rate through dissolution of tabular forsterite. The tabular morphology of jack-straw olivine is a consequence of twin-mediated unidirectional growth; the abundance of twins being due to rapid nucleation and growth at initially high reaction affinities. Twin junctions are preferential nucleation centers for steps, so faceted growth is enhanced on {100}. This phenomenon is the twin plane re-entrant effect. Subequant polyhedral forsterite in the Ubehebe Peak inner contact aureole recrystallized and ripened from tabular forsterite. In the outer contact aureole, conditions were not conducive to recrystallization and ripening so well-developed tabular forsterite persists.

Bi‐Directional Growth of Thin Films: Unlocking Anisotropic Ferromagnetism and Superconductivity

AbstractThe pursuit of breakthroughs in thin film technology drives the exploration of novel growth strategies for quantum materials that surpass conventional limitations. Departing from the prevailing unidirectional growth approach, the methodology allows for atomic precision in both the in‐plane and out‐of‐plane directions. To demonstrate the capabilities of this transformative technique, a bi‐directionally grown superlattice comprised of alternating LaMnO3 and SrMnO3 layers is engineered, enabling the emergence of interfacial ferromagnetism. By adopting this superlattice as a model system, the vast potential of the approach is highlighted through comprehensive analysis and characterization. Furthermore, the application of the method is extended to the growth of superconducting La1.84Sr0.16CuO4 thin films on various offcut substrates. Remarkably, these substrates induce an anisotropic critical current originating from two distinct mechanisms.

Trends In Extreme Weather Events With Socio-Economic Damage Over The Period 1991-2019 In Russia And Its Regions

Increased number of extreme weather events is one of the most serious hazards of climate change over the territory of Russia. However, there is a lack of comprehensive analysis of the number of extreme weather events that caused social and economic damage in the country and its regions. This paper analyzes changes in the total number of events with damage (meteorological for the period 1991-2019 and agrometeorological – for 2004-2019), disaggregated by their types and by regions. The Mann-Kendall test is applied to detect statistical significance (0.05 level of significance, normal distribution). The results show an increase in the number of meteorological extreme events with damage for 1990-2019 in Russia from 130 to 257 events per year on average for the 1990s and 2010s, respectively, while the proportion of events with damage in relation to the total number of extreme events decreased over this period. We found statistically significant trends only for a few types of extreme events: hot and cold temperature, strong wind, heavy rain and droughts (increase by 0.9, 9.4, 11.4, 25.9 and 13.3 events/10 years, respectively). Number of heavy rain precipitation events is the only unidirectional stable growth trend. Unusual increasing trend in cold extreme events with damage in Russia can be attributed to the greater damage to the economy and population from cold extremes than hot ones. The regional distribution of trends across the territory of the Russian Federation is heterogeneous. However, significant changes in the number of extreme events of strong winds, heavy rains and soil drought by regions are statistically positive and observed mostly in some southern and central regions of European part and the Western Siberia. The development of adaptation plans to the negative effects of climate change is a first priority for these regions. A system for monitoring economic and non-economic damage from extreme events must be developed in Russia.

Unidirectional growth of epitaxial tantalum disulfide triangle crystals grown on sapphire by chemical vapour deposition with a separate-flow system

Tantalum disulfide has been attracting considerable attention due to its rich phase diagram that includes polytypes and charge density waves, thus having potential for electrical device applications.

Essential Role of Anisotropy in Bioengineered Cardiac Tissue Models.

As regulatory bodies encourage alternatives to animal testing, there is renewed interest in engineering disease models, particularly for cardiac tissues. The aligned organization of cells in the mammalian heart controls the electrical and ionic currents and its ability to efficiently circulate blood to the body. Althoughthe development of engineered cardiac systems is rising, insights into the topographical aspects, in particular, the necessity to design in vitro cardiac models incorporating cues for unidirectional cell growth, is lacking. This review first summarizes the widely used methods to organize cardiomyocytes (CMs) unidirectionally and the ways to quantify the resulting cellular alignment. The behavior of CMs in response to alignment is described, with emphasis on their functions and underlying mechanisms. Lastly, the limitations of state-of-the-art techniques to modulate CM alignment in vitro and opportunities for further development in the future to improve the cardiac tissue models that more faithfully mimic the pathophysiological hallmarks are outlined. This review serves as a call to action for bioengineers to delve deeper into the in vivo role of cellular organization in cardiac muscle tissue and draw inspiration to effectively mimic in vitro for engineering reliable disease models.

Optimizing optical and antimicrobial properties of europium-doped copper sulphate pentahydrate crystal via unidirectional growth and characterization

A Europium-doped Copper Sulphate Pentahydrate crystal was grown using Unidirectional growth method, resulting in a crystal that was 108 mm long. Various characterization methods were employed to investigate its growth, optical, structural, and antimicrobial properties. X-ray Diffraction analysis showed that the crystal belonged to the P1 space group and calculated its corresponding lattice parameters. The band gap of the grown crystal was determined by analysing its response to UV excitation. Fourier transform infrared spectroscopy identified the presence of OH and sulfoxide bond. Surface images of the crystal were taken using the Scanning electron microscope, and EDAX reports confirmed the presence of Europium in the grown crystal. Photoluminescence studies showed the emission peak at 640 nm, and 5D0 to 7FJ (J = 2,3) transition levels were observed in the emission spectrum corresponding to europium ions in the orange-red region using 320 nm of excitation wavelength. Antimicrobial studies were conducted on Eu doped CuSO4·5H2O crystals using two gram-positive, two gram-negative bacteria, and two fungal cultures. The zone of inhibition was measured and found to be 12,12,13.5,14 mm and 16,17 mm for Staphylococcus aureus, Enterococcus Faecalis, Escherichia coli, Klebsiella pneumoniae, and Candida, Aspergillus, respectively. These findings indicate that Eu doped CuSO4·5H2O is a fast-growing crystal that exhibits good quality optical and antimicrobial activity.

Unidirectional growth of polyaniline on 3D CoO nanowires for aqueous asymmetric supercapacitors

Metal oxide-based binary nanohybrids are a new class of binder-free supercapacitor electrodes. This paper reports the enhanced electrochemical performance of polyaniline (PANI)/CoO nanowires grown on Ni foam for use in aqueous asymmetric supercapacitors (SCs). Several synthetic parameters were optimized for the unidirectional growth of PANI on CoO nanowires. The rationally designed core-shell structured electrode exhibited a high specific capacity of 1113C g−1 (specific capacitance of 2473 F g−1) at a current density of 3 A g−1 and good cycling stability of 86.3 % over 10,000 charge/discharge cycles in a 1 M KOH electrolyte through a substantial synergistic contribution from each component. In addition, an aqueous asymmetric supercapacitor based on these PANI/CoO nanowire arrays exhibited a high specific energy of 35.8 Wh kg−1 and high cycling stability (89.1 % after 5000 cycles). Two aqueous asymmetric supercapacitors connected in series could light up 19 red light-emitting diodes (LEDs). Therefore, this electrode can be considered a superior candidate for the next-generation SC electrodes.

Microstructure and mechanical properties of functional gradient materials of high entropy alloys prepared by direct energy deposition

In this study, FeCrCoNiMo0.5W0.75 HEAs functional gradient materials were prepared by the direct energy deposition (DED) technique, and the phase transition, microstructure and mechanical properties of the materials along the building direction were investigated. The material realizes a transition from a single FCC phase to an FCC + TCP phase from the bottom to the top. The bottom and middle of the material are typical dendritic (DR)-interdendritic (ID) structures, and at the top, due to the precipitation of the eutectic structure σ phase and μ phase, the material transforms into a hypoeutectic structure of FCC + eutectic. According to the EBSD results, the interior of the material is mainly columnar crystals that grow vertically to the molten pool. This unidirectional columnar growth makes the material have a strong texture in the <100> direction. In addition, a large degree of grain refinement is exhibited from the bottom to the top, with the grain size reduced from 19 μm to 6.5 μm. According to the TEM results, the density of dislocations is much higher near the phase and grain boundaries than in other regions, and dislocation entanglement is formed by the continuous accumulation of loose dislocations. The micro-hardness of the material increased along the construction direction up to 892.5HV0.5, and the material has good compressive strength up to 2041 ± 45 MPa. The material has excellent wear resistance and high-temperature wear resistance, forming a continuous oxide layer at 800 °C, which greatly reduces the friction coefficient and wear rate.

Extracellular transfer of a conserved polymerization factor for multi-flagellin filament assembly in Caulobacter

Unidirectional growth of filamentous protein assemblies including the bacterial flagellum relies on dedicated polymerization factors (PFs). The molecular determinants and structural transitions imposed by PFs on multi-subunit assembly are poorly understood. Here, we unveil FlaY from the polarized α-proteobacterium Caulobacter crescentus as a defining member of an alternative class of specialized flagellin PFs. Unlike the paradigmatic FliD capping protein, FlaY relies on a funnel-like β-propeller fold for flagellin polymerization. FlaY binds flagellin and is secreted by the flagellar secretion apparatus, yet it can also promote flagellin polymerization exogenously when donated from flagellin-deficient cells, serving as a transferable, extracellular public good. While the surge in FlaY abundance precedes bulk flagellin synthesis, FlaY-independent filament assembly is enhanced by mutation of a conserved region in multiple flagellin paralogs. We suggest that FlaYs are (multi-)flagellin PFs that evolved convergently to FliDs yet appropriated the versatile β-propeller fold implicated in human diseases for chaperone-assisted filament assembly.